The present invention relates to an angle sensor for sensing the angular position of a steerable wheel on a vehicle, wherein the sensor is mounted to be concentric with and internally connected to the kingpin that pivotally mounts a wheel hub to a fixed hub on the axle.
A steerable wheel industrial loader and its controls are described in copending U.S. Application entitled Selectable Control Parameters on Power Machine, Ser. No. 09/733,221, filed Dec. 8, 2000, the disclosure of which is incorporated by reference.
In modern steerable industrial vehicles, the wheels may be independently supported and independently steerable, and it is necessary to have coordinated steering angles between front and rear wheels, as well as between the wheels on the same axle but on opposite sides of the wheels. Computer controls are able to resolve signals indicating steer angle differences, and make adjustments to the steering system for appropriate matching angles, or if desired, providing different angles of certain wheels for various purposes.
In order to accurately control the steering angle of a steerable wheel, the angle must be sensed correctly. The sensor also has to be located so that it is not damaged by external conditions, such as rocks or shaking, bumping or the like.
Angle sensors have been known for years, and the Torrington Company makes various angle sensors that are highly reliable and compact. Many of these are solid state sensors that will sense angles between a stationary housing and a rotatable stem or drive shaft very accurately, and reliably, with low power consumption.
The present invention relates to an angle sensor for sensing the angular position of a steerable wheel and hub relative to a reference position, normally the longitudinal axis of a vehicle. The angle sensor is mounted in a bore in and made a part of the kingpin that supports the rotating wheel hub to its fixed wheel support housing on the axle of the vehicle. The sensor has fully protected rotatable parts that are rotated relative to each other about the axis of the kingpin when the wheel is steered.
The kingpin structure is a headed pin that is passed through bores in aligning parts that overlap so that the wheel hub, which has an annular support ring with top and bottom pads with bores for the kingpins, is held onto mating ears on the fixed wheel support housing on the axle. There are king pins on both the top and bottom of the wheel hub. One king pin has an axial bore with an insert shaft having a drive tang or coupling that engages a rotatable shaft of an angle sensor that is mounted in a recess in the other end of the kingpin. The sensor housing is mounted on an arm supported on the stationary wheel support housing. The kingpin will rotate with the wheel hub as the wheel is steered, and will drive the rotatable shaft of the angle sensor. The angle sensor housing remains fixed so that relative rotation can be sensed.